An integrated biomass-to-algae pathway for producing emergency food components from lignocellulosic waste

Global food systems are highly vulnerable to catastrophic disruptions, highlighting the need for alternative food sources that do not rely on conventional crop production. Lignocellulosic biomass is an abundant non-food resource with substantial stored energy, but it is not directly edible by humans. We present an integrated bioconversion strategy that converts lignocellulosic biomass into three essential macronutrients. Lime [Ca(OH)₂] pretreatment solubilizes lignin and deacetylates hemicellulose to liberate soluble acetate, facilitating subsequent enzymatic cellulose hydrolysis. This acetate-rich liquid supports the growth of an edible alga, Chlamydomonas reinhardtii, under low light, producing 835-971 mg/L cell mass with 30-31% lipid content, approximately twice that of standard medium. The algal biomass contained 5-10% protein, while the remaining solid lignocellulosic residue yielded up to 22% glucose upon enzymatic hydrolysis, twice that from untreated biomass. These results show that lime-treated lignocellulosic biomass can be fractionated into glucose-rich hydrolysates and acetate-derived algal biomass enriched in lipids, although protein production remains limited. Life-cycle and techno-economic analyses indicate that this biomass-based algal system is environmentally and economically viable, offering a resilient food source under extreme conditions, although further optimization is needed to improve protein yield and practical scalability.